Count number of of comma separate values

Count number of of comma separate values

Hi all, 

I'm wondering if there's a way of counting the number of comma separated values in a field?

My report looks like this.

I would like to count the number of 'participation dates' for each person and keep a running total in the 'Number of attendances field'. The 'participation date' is a bidirectional lookup field whereby when a person is selected from a lookup in the 'participation form', the date that they participated is shown here. 

So Bill Smith = 0
John Day = 4
etc. 

Is this possible? Or could someone suggest a better way?

Thanks!

Lindsay